Derive the step base for an input element as (now) specified.

Source/core/html/forms/InputType.cpp

 /*
  * Copyright (C) 1999 Lars Knoll (knoll@kde.org)
  *           (C) 1999 Antti Koivisto (koivisto@kde.org)
  *           (C) 2001 Dirk Mueller (mueller@kde.org)
  * Copyright (C) 2004, 2005, 2006, 2007, 2008, 2009, 2010, 2011 Apple Inc. All rights reserved.
  *           (C) 2006 Alexey Proskuryakov (ap@nypop.com)
  * Copyright (C) 2007 Samuel Weinig (sam@webkit.org)
  * Copyright (C) 2009, 2010, 2011, 2012 Google Inc. All rights reserved.
  * Copyright (C) 2012 Samsung Electronics. All rights reserved.
  *
@@ skipping 408 matching lines @@
     }
 
     return emptyString();
 }
 
 bool InputType::shouldSubmitImplicitly(Event* event)
 {
     return event->isKeyboardEvent() && event->type() == EventTypeNames::keypress && toKeyboardEvent(event)->charCode() == '\r';
 }
 
-Decimal InputType::parseToNumber(const String&, const Decimal& defaultValue) const
+Decimal InputType::parseToNumber(const String&, const String&, const Decimal& defaultValue) const
 {
     ASSERT_NOT_REACHED();
     return defaultValue;
 }
 
 Decimal InputType::parseToNumberOrNaN(const String& string) const
 {
-    return parseToNumber(string, Decimal::nan());
+    return parseToNumber(string, String(), Decimal::nan());
 }
 
 bool InputType::parseToDateComponents(const String&, DateComponents*) const
 {
     ASSERT_NOT_REACHED();
     return false;
 }
 
 String InputType::serialize(const Decimal&) const
 {
@@ skipping 531 matching lines @@
 
 void InputType::countUsageIfVisible(UseCounter::Feature feature) const
 {
     if (RenderStyle* style = element().renderStyle()) {
         if (style->visibility() != HIDDEN)
             UseCounter::count(element().document(), feature);
     }
 }
 
 } // namespace WebCore